Multiring seal for obturating the breech of large caliber guns



March 9 9 R. J. THIERRY 3,434,381

MULTIRING SEAL FOR OBIURATING THE BREECH 0F LARGE CALIBER GUNS Filed April 23. 1968 I Sheet of 5 INVENTOR March 25, 1969 J THlERRY 3,434,381

- MULTIRING SEAL FOR OBTURATING THE BREECH 0F LARGE CALIBER GUNS Filed April 23, 1968 Sheet 3 of 3 INVENTOFZ EELEL Ember QLThierry BY v y P Q 80 ATTORNEY 3,434,381 MULTIRING SEAL FOR OBTURATING THE BREECH 0F LARGE CALIBER GUNS Robert J. Thierry, Averill Park, N.Y., assignor to the United States of America as represented by the Secretary of the Army Filed Apr. 23, 1968, Ser. No. 723,468 Int. Cl. F41f 11/08 US. C]. 89-26 16 Claims ABSTRACT OF THE DISCLOSURE In a large caliber gun of the type wherein the breech is closed by the sliding actuation of the breechblock at a slight angle to the transverse axis of the tube, the sealing of the closed breech is accomplished by a multiring assembly seated in the front face of the breechblock and composed of an elastomeric ring surrounded by a metallic backup ring which is, in turn, surrounded by a metallic camming ring. During the closing of the breech, the backup ring wipes the breech face of the gun tube to remove any foreign matter therefrom while the camming ring acts to preload the backup and elastomeric rings and thereby increase the ability thereof to seal the breech under the peak pressures produced during the firing of the gun.

The invention described herein may be manufactured and used by or for the Government for governental purposes without payment to me of any royalty thereon.

This invention relates to means for sealing the breech of large caliber guns during firing and is more particularly directed to an improved ring seal of the type wherein the end face thereof is utilized as the sealing surface.

In order to increase the rate of fire of large caliber guns, current design efforts are being directed to the use of caseless ammunition which does not require a metallic case to contain the propellant charge and therefore eliminates the time-consuming steps of extracting the fired case from the firing chamber and ejecting it from the gun. While such simplification of the operating cycle does provide a significant increase in the rate of fire, the elimination of the metallic case results in an increase in the temperatures and pressures encountered in the breech area which complicates the required sealing of the breech against the loss of firing pressure.

For one thing, the higher breech pressures encountered in the firing cycle of the longer range weapons now under development produce a corresponding increase in the gap which normally exists between the front face of the breechblock and the rear face of the gun tube. Such gap is initially created by the necessity for reasonable tolerances which will permit economical manufacture of the breechblock and the gun tube and is enlarged as these components are forced apart in opposite directions in response to the pressures generated in the breech area during, firing. Since these firing pressures produce unsymmetrical bending of the breechblock and since the latter is generally forced rearwardly to a greater extent than the concurrent forward movement of the gun tube relative to the breech ring, considerable difficulty has been experienced in maintaining adequate contact between the outer periphery of a ring seal and the surfaces on both sides of the gap, especially since some breech designs are known to permit gaps as large as .050 inch.

It is therefore apparent that the prior art dependency on the outer periphery of a ring seal for sealing the gap between the breechblockand the gun tube is no longer adequate. Accordingly, the breech structures of some guns have been designed to utilize the larger contact surface afforded by the end face of a ring seal in order to ac- United States Patent 0 complish the required degree of sealing. However, since caseless ammunition is not always entirely consumed upon firing, these larger sealing surfaces are more prone to the accumulation of unburnt combustion products. In addition, the act of loading the ammunition into the firing chamber of the gun frequently produces scratches and nicks in the surface to be sealed which, in conjunction with the tool marks generally present thereon, renders it extremely difiicult for a metallic ring to provide adequate sealing contact with the mating metallic surface on the breech face of the gun tube. Furthermore, the loading of the ammunition also introduces particles of dust and dirt into the breech area which adhere to the powder residue accumulation and increase the interference with the sealing function of these metallic ring seals. Any deterioration in the tight contact required between a ring seal and the surface to be sealed is extremely critical since the corrosive nature of the high velocity discharge gases and the high temperatures and pressures encountered in guns of current design is such that even a very slight leakage is enough to destroy the effectiveness of the ring seal, often within a few firing cycles.

Although attempts have been made to utilize ring seals fabricated from elastomeric rather than metallic materials in order to overcome the slight leakage caused by foreign matter and defects on the surfaces to be sealed, these attempts have not been successful primarily because of the tendency for these elastomeric materials to extrude into the relatively large gap which is frequently produced between the breechblock and the gun tube during firing. Obviously, any failure of the ring seal to return to its original configuration will interfere with the subsequent proper opening and closing of the breech. In addition, the deteriorating effect of any permanent deformation of these elastomeric seals rapidly leads to a complete failure thereof.

Accordingly, it is a general object of this invention to provide an improved breech seal particularly adapted for use in those guns wherein the breechblock is slidably actuated into battery position in a direction transverse to the longitudinal axis of the gun tube.

It is a further object of the present invention to provide a breech seal in the form of a ring which can be mounted in a recess in the forward end of the breechblock so that the end face of the ring will contact the rear face of the gun tube to effect the sealing action.

Another object of this invention is to provide a ring type of breech seal which will be strong enough to resist permanent deformation under the higher pressures and temperatures encountered in high rate of fire guns which utilize caseless ammunition.

Still another object of the present invention is to provide a breech seal as aforesaid which will effect positive sealing even though combustion products and other foreign matter adhere to the sealing surfaces on the breechblock and gun tube.

A further object of this invention is to provide an improved breech seal, as aforesaid, which will continue to function effectively despite any increase, during firing, in the gap which normally exists between the front face of the breechblock and the rear face of the gun tube.

A more specific object of the present invention is to provide a multiring type of breech seal which will be sufficiently elastic to completely seal the irregular surface created by the adherence of combustion products and other foreign matter and yet be sufiiciently rigid to resist extrusion into the gap between the front face of the breechblock and the rear face of the gun tube.

It it another object of this invention to provide a breech seal as aforesaid which can be mounted in the breechblock so as to protrude sufficiently from the front face action along a portion of the rear face of the gun tube in order to minimize the accumulation of foreign matter thereon.

A final object of the invention is to provide a breech seal as aforesaid which will be automatically preloaded during the breech closing movement of the breechblock so that effective sealing will start concurrently with the initial rise in the firing pressure.

It has been found that these objects can be attained by the provision of a multiring seal comprising an obturating ring of elastomeric material having a sloping outer periphery slidably seated against the mating beveled face of an inner metallic ring which is, in turn, similarly seated against the beveled face of an outer metallic ring. This combination of rings is mounted in a cylindrical recess in the front face of the breechblock and is held in nested relation by an annular retainer fixedly secured in the breechblock in abutment with the inner periphery of the obturating ring. The inner ring is arranged to normally protrude forwardly beyond both the obturating and outer rings so that as the breechblock is lifted into battery position at a slight angle to the vertical axis thereof, such inner ring is pressed against the breech face of the gun tube with a constantly increasing force. The resulting wiping action on the gun tube surface to be sealed minirnizes the accumulation of powder residue and other foreign matter thereon. At the same time, the angular relationship between the mating surfaces of the three rings causes the outer ring to compress the inner ring which, in turn, compresses the obturating ring to move forwardly into sealing contact with the breech face of the gun tube. As a result, by the time the breechblock reaches battery position both the inner and obturating rings are preloaded in a manner which not only increases the reslstance thereof to deformation by the rising pressures in the firing chamber but also compresses the elastomeric obturating ring to completely envelop any foreign matter remaining on the breech face of the gun tube. As the breechblock and gun tube are forced in opposite directions by the rapidly expanding discharge gases, the firi ng pressure retains the outer ring in frictional contact with the sidewalls of the sealing ring recess in the breechblock. Thus, as the outer ring moves rearwardly together with the breechblock the pressure of the discharge gases on the inner ring will cause it to be cammed forwardly as well as outwardly against the outer ring to compensate for any forward movement of the gun tube relative to the breech ring and maintain the required maximum sealing contact.

The exact nature of the invention as well as other objects and advantages thereof will be readily apparent from consideration of the following specification relating to the annexed drawing wherein:

FIG. 1 is a vertical section through the breech area of a large caliber gun provided with a vertically slid ng breechblock, the multiring seal of the present lnvention being shown in the firing position thereof;

FIG. 2 is a greatly enlarged cross-sectional view of the breech area showing the relationship of the seal components immediately prior to contact with the breech face of the gun tube during the breech closing movement of the breechblock;

FIG. 3 is a view similar to that of FIG. 2 but showing the position of the component parts of the seal at the conclusion of the breech closing movement of the breechblock;

FIG. 4 is a view similar to that of FIGS. 2 and 3 but showing the position of the components of the seal during the peak pressure generated upon the firing of a round of caseless ammunition;

FIG. 5 is an enlarged view, taken along line 55 in FIG. 1, of a preferred arrangement for retaining the seal in the breechblock; and

FIG. 6 is an exploded perspective view of the seal as- 4 i elmbly drawn to substantially the same size as that of As best shown in FIG. 1, the gun in which the multiring seal of the present invention is utilized includes a breech ring 12 which is threadably secured, as shown at 14, to the breech end of a gun tube 16 containing a firing chamber 17 adapted for the firing of caseless ammunition. A rectangular opening 18 is vertically provided through breech ring 12 for slidably receiving a correspondingly shaped breechblock 20 having vertical ribs 22 on opposite sides thereof fitting in mating slots 24 formed into the side walls of breech ring opening 18. Ribs 22 and slots 24 are both slightly inclined relative to the vertical axis of breechblock 20 in order to permit the entire front face thereof to close squarely against the breech end face of gun tube 16 with a minimum of sliding friction. The vertical actuation of breechblock 20 during the opening and closing movements thereof is achieved by means of a crank lever 26 rotatably mounted at one end between a pair of spaced apart lugs 28 depending from the underside of breech ring 12, only one of such lugs being shown in FIG. 1. The other end of lever 26 is operatively engaged with breechblock 20 by means of a conventional roller and cam track arrangement as indicated at 30 and 32 respectively. As lever 26 is pivoted by suitable means (not shown) during the recoil and counter recoil travel of breech ring 12, breechblock 20 is lowered and raised to respectively open and close the breech.

The front face of breechblock 20 is provided with a centrally disposed annular groove 34 therein which serves as a seat for the multiring seal assembly 36. Groove 34 is slightly increased in depth along the outer portion thereof, as indicated at 38, in order to provide an expansion area for the discharge gases generated upon the firing of the gun. Retention of seal assembly 36 in groove 34 is achieved by an annular insert 40 which is fixedly mounted therein by a plurality of screws 42 threadably engaged in breech ring 12. Screws 42 are provided with enlarged heads 44 which seat in suitably countersunk holes 46 radially spaced about the front face of insert 40. The cross-sectional thickness of retainer insert 40 is greatly reduced outwardly of holes 46 to form a flanged rim 48 with a rearwardly sloping outer edge 50 adapted to contact the correspondingly sloped inner periphery '52 of an obturating ring 54 for preventing tilting or forward movement thereof in groove 34. A plurality of arcuately elongated gas passages 56 are radially spaced about flanged rim 48 outwardly of countersunk holes 46 to facilitate the entry of the discharge gases into annular groove 34 for energizing seal assembly 36.

Obturating ring 54 is fabricated from an elastomeric material such as Teflon or Kel-F and is angularly sloped along the entire outer periphery thereof as indicated at 58. The inner periphery 52 of ring 54 is connected to the outer periphery 58 thereof by an angular surface forming a beveled counterbore 60 which facilitates the flow of the discharge gases into the interior of annular groove 34. Surrounding obturating ring 54 is an inner sealing ring 62 preferably fabricated of a relatively tough and hard alloy steel and provided with a beveled inner periphery 64 which provides a slip fit with the correspondingly sloped outer periphery 58 of ring 54. Inner ring 62 is similarly surrounded by an outer sealing ring 66 of alloy steel wherein the outer periphery '68 thereof is contoured to mate with the arcuately joined interior wall surfaces of groove 34. The inner periphery of ring 66 is beveled as indicated at 70 to mate with the correspondingly sloped outer periphery 72 of inner ring 62.

The diameters of the inner and outer peripheries of rings 54, 62, and 66 and the particular slopes of such peripheries are so related that, prior to contact with the breech end face of gun tube 16, both inner sealing ring 62 and obturating ring 54 are seated to protrude forwardly beyond the front end face of outer sealing ring 66 with inner ring 62 protruding slightly beyond obturating ring 54, as best shown in FIG. 2. Any increase in such initial protrusion is prevented by the relationship between sloped surfaces 50 and 72 of flanged rim 48 and outer ring '66 respectively. However, inner ring 62 can be set to provide as much as .040 inch of protrusion beyond outer ring 66. As a result, the beneficial preloading of the seal can be attained without any costly reduction in the manufacturing tolerances of the various components of the breech structure.

As breechlock is lifted by crank lever 26 to close the breech, the angular inclination of vertical ribs 22 thereon simultaneously advances breechblock 20 toward full contact with the breech end face of gun tube 16, as best shown in FIG. 3. Thus, once inner ring 62 contacts the breech end face of gun tube 16, the continued upward movement thereof creates a constantly increasing wiping force against the surfaces to be sealed which effectively reduces the customary accumulation of unburnt powder residue and other particles of foreign matter thereon. As a result, the formation of gas leakage paths between the surfaces to be sealed is kept to a minimum. As such desirable wiping action is being effected, the forward movement of breechblock 20 also advances outer sealing ring 66 to axially compress inner sealing ring 62 which, in turn, similarly compresses obturating ring 5-4. Thus, obturating ring 54 is forced into contact with the breech end face of gun tube 16 to provide an additional wiping action thereon in conjunction with that of inner sealing ring 62. When the breechblock 20 reaches the battery position shown in FIG. 3 and is locked therein by suitable means not shown, obturating ring 54 and inner sealing ring 62 are both preloaded in compression. Thus, any foreign matter which may still remain on the breech end face of gun tube 16 is crushed by inner sealing ring 62 and enveloped by the elastomeric material of obturating ring Accordingly, when a chambered round of ammunition 73 is fired by suitable means indicated generally at 74, the increasing gas pressure must first counteract the compressive stresses on obturating ring 54 and on inner sealing ring 62 before any tensile stresses can be imparted thereto. As a result, rings 54 and 62 are able to withstand an appreciable higher total stress without permanent deformation than would be the case if no preloading was provided.

As the volume of the discharge gases rapidly increases after firing is initiated, rings 54 and 62 are stressed in tension and are simultaneously forced against the sealing surfaces on the breech end of tube 16 to provide the degree of contact required to withstand the peak firing pressure. In the event of any slight clearance between inner sealing ring 62 and the breech end face of gun tube 16 due to unburnt powder residue or other particles of foreign matter, the flexibility of obturating ring 54 will permit it to assume the major portion of the sealing action. In such case, the function of ring 62 is primarily that of a backup for ring 54. The sealing ability of obturating ring 54 is not diminished by the existence of any scratches or nicks on the surface area being sealed since the elastomeric material thereof will readily expand to fill up the depressions formed by such scratches and nicks.

As the pressure of the discharge gases continues to increase, the clearances between breechblook 20 and rectangular opening 18 in breech ring 12 and between threads 14 are taken up and result in a corresponding rearward movement of breechblock 20* which produces a significant gap between the front face thereof and the breech end face of tube 16. In some instances, the peak pressure of the discharge gases may be enough to produce actual deflection of threads 14 as Well as unsymmetrical bending of breechblock 20 and lugs 28 on breech ring 12. In such cases, the gap between breechblock 20 and tube 16 has been known .to reach as much as .050 inch in size. Since the force which presses outer ring 66 against the walls of annular groove 34 is greater than the force pressing such ring against the breech end face of gun tube 16, the rearward movement of the breechblock 20 during the opening of the gap with tube 16 will carry ring 66 away from sealing contact therewith. However, since ring 66 provides very little or no sealing action against the breech end face of gun tube 16, no significant reduction in the extent of the total sealing ability of the assembly will take place. In fact, if the transverse wall surface of groove 34 was :provided with a slope similar to that of the outer periphery of inner ring 62, outer ring 66 could, in most instances, be eliminated from the assembly. During the rearward movement of outer ring 66, the pressure of the discharge gases on the exposed portion of the inner periphery thereof and the sloped contact thereof with inner ring 62 holds the latter in sealing contact with the breech end face of gun tube 16 and also serves to prevent the leakage of any gases between seals 62 and 66. Once the gas pressure has passed its peak and begins to fall, inner ring 62 and obturating ring 54 are restored to their original configuration and consequently do not interfere with the subsequent breech opening movement of breechblock 20.

Thus, there is here provided a superior multiring seal 'which will effectively obturate the gap between the face of the breechblock and the breech end of the gun tube despite the existence of any foreign matter or defects on the surfaces to be sealed. In addition, such sealing will be accomplished without permanent deformation of the seal components even though the size of the gap between the breechblock and the gun tube changes in response to the rise and fall of the gas pressures produced during the firing of a caseless round of ammunition. Furthermore, the seal components are specifically designed to be preloaded during the closing and locking of the breech to an extent which will permit a high level of sealing at the very beginning of the rise in the gas pressure produced by the firing of the ammunition. Such preloading also increases the resistance of the components to permanent deformation inasmuch as the initial compressive stresses thereon must be fully overcome before any tensile stresses are imparted thereto by the continuing rise of gas pressure. Moreover, the combining of elastomeric and metallic rings in the manner described herein provides a seal which possesses a relatively long endurance life and a flexibility of operation which will handle the variety of problems encountered in sealing large caliber guns firing caseless ammunition.

I claim:

1. In a gun having a tube with a firing chamber in the breech end thereof and a slidable breechblock for opening and closing the breech end of the tube in a direction transverse to the longitudinal axis thereof and at a slight angle relative to the end face of the tube, the improvement comprising:

a plurality of sealing rings vertically disposed within the front face of the breechblock in nested peripheral contact,

means for positioning at least one of said rings to protrude forwardly from the breechblock,

mating cam surfaces between each of said rings, and

means for slidably retaining said rings within the breechblock whereby the angular breech closing movement thereof first advances said forwardly protruding ring into wiping contact with the breech face of the gun tube and thereafter advances said ring adjacent said protruding ring to provide a camming action therebetween which induces compressive stresses therein for increasing the resistance thereof to the tensile stresses subsequently imparted thereto upon the firing of the gun.

2. The structure set forth in claim 1 wherein said cam surfaces between said protruding ring and said ring adjacent thereto includes a surface integral with the breechblock.

3. The structure defined in claim 1 wherein said plurality of rings includes an inner ring of elastomeric material adjacent the inner perphery of said protruding ring, and

an outer ring of alloy steel adjacent the outer periphery of said protruding ring.

4. The structure of claim 1 wherein said means for retaining said rings in the breechblock comprises an annular member fixedly secured in the breechblock and provided with a forwardly and upwardly inclined surface for contact with one of said rings adjacent said forwardly protruding ring.

5. In a gun having a tube with a firing chamber in the breech end thereof, a slidable breechblock for opening and closing the breech end of the tube transversely of the longitudinal axis thereof, means for angularly advancing the breechblock during the breech closing movement thereof to provide full initial contact with the breech end face of the gun tube, and means for sealing the junction between the front face of the breechblock and the breech end face of the tube against the discharge gases in the firing chamber, comprising:

a first metallic sealing ring seated in the front face of the breechblock for joint movement therewith,

a second metallic sealing ring slidably surrounded by said first sealing ring in camming engagement therewith,

an obturating ring of elastomeric material surrounded by second sealing ring, and

a retainer for holding said rings in assembled relation and against forward movement relative to the breechblock whereby the angular breech closing movement thereof advances said first sealing ring to compress said second sealing ring which, in turn, compresses said obturating ring thereby inducing stresses in both of said rings which serve to counteract the initial portion of the tensile stresses imparted thereto upon the firing of the gun.

6. The structure set forth in claim 5 wherein said first sealing ring is integral with the breechblock.

7. The structure defined in claim 5 wherein said second sealing ring protrudes from the front face of the breechblock beyond said first ring and said obturating ring to effect a wiping action on the breech end face of the gun tube during the breech closing movement of the breechblock.

8. The structure of claim 5 wherein said retainer comprises an annular member fixedly secured in the front face of the breechblock and provided with a flanged outer rim in contact with said obturating ring, said annular member being also provided with a plurality of radially spaced openings therethrough for the passage of discharge gases against said obturating and sealing rings.

9. In a gun having a tube with a firing chamber in the breech end thereof, a breech ring threadably secured to the breech end of the tube, a breechblock slidably mounted in the breech ring for opening and closing the breech end of the tube transversely of the longitudinal axis thereof, means in the breech ring for angularly advancing the breechblock during the breech closing movement thereof to provide full initial contact with the breech end face of the tube, and improved means for sealing the junction between the front face of the breechblock and the breech end face of the tube against the discharge gases generated in the firing chamber, comprising:

an obturating ring of elastomeric material,

an inner sealing ring surrounding said obturating ring,

an outer sealing ring seated in the front face of the breechblock to surround said inner sealing ring in slidable contact therewith,

means for retaining said obturating and said inner and outer rings in assembled relation and against forward movement relative to the breechblock, and

angular mating surfaces between said obturating ring and said inner sealing ring and between said inner and outer sealing rings whereby the angular breech closing movement of the breechblock actuates said outer sealing ring to compress said inner sealing ring and thereby said obturating ring for inducing stresses therein which will counteract the initial portion of the tensile stresses imparted thereto upon the firing of the gun.

10. The structure set forth in claim 9 wherein the front face of the breechblock is provided with a centrally disposed annular groove for seating said outer sealing ring therein, and said inner sealing ring is seated against said outer sealing ring to expose a portion thereof to the pressure of the discharge gases generated in the firing chamber and thereby assist said angular mating surfaces therebetween in retaining said outer sealing ring in said annular groove against movement relative to the breechblock.

11. The structure in accordance with claim 9 wherein said obturating ring is provided with a beveled counterbore in the rear face thereof and a beveled inner periphery of lesser slope which in conjunction with said beveled counterbore permits the discharge gases to force said obturating ring against said inner sealing ring and forwardly against the breech end face of the gun tube.

12. The structure defined in claim 9 wherein said outer sealing ring is substantially flush with the front face of the breechblock and said inner sealing ring protrudes beyond both said obturating and outer sealing rings to effect a wiping action on the breech end face of the gun tube during the breech closing movement of the breechblock.

13. The structure of claim 9 wherein said means for retaining said obturating and said inner and outer rings in assembled relation comprises an annular member fixedly secured centrally within the front face of the breechblock, said member having a flanged portion of reduced cross-section terminating in a sloped outer rim in contact with said obturating ring, and

gas passage means through said flanged portion for admitting discharge gases against said obturating and said inner and outer sealing rings.

14. In a gun having a tube containing a firing chamber in the breech end thereof, a breech ring threadably secured to the breech end of the tube, a breechblock slidably mounted in the breech ring for opening and closing the breech end of the tube transversely of the longitudinal axis thereof, the breechblock being provided with a centrally disposed annular groove in the front face thereof, and means in the breech ring for angularly advancing the breechblock during the breech closing movement to provide a squared initial contact thereof with the breech end face of the tube, the improvement of means for sealing the junction between the front face of the breechblock and the breech end face of the tube against the discharge gases generated in the firing chamber, comprising, in combination,

an obturating ring of elastomeric material having a beveled inner periphery and an angular outer periphery of greater slope than said inner periphery,

a metallic inner sealing ring having a beveled inner periphery surrounding said outer periphery of said obturating ring in slidable mating contact therewith and an angular outer periphery of lesser slope than said inner periphery,

a metallic outer sealing ring having a beveled inner periphery surrounding said outer periphery of said inner sealing ring in slidable mating contact therewith and a substantially transverse outer periphery in contact with the corresponding circumferential wall surface of the annular groove in the breechblock, and

an annular retainer fixedly secured in the annular groove in the front face of the breech block having a sloped rim for mating contact with said angular inner periphery of said obturating ring to hold said rings in assembled relation and against forward movement relative to the breechblock whereby the angular breech closing movement thereof advances said outer sealing ring to compress said inner sealing ring which, in turn, compresses said obturating ring thereby preloading said inner and obturating rings to counteract the initial portion of the tensile stresses imparted thereto upon the firing of the gun.

15. The structure as set forth in claim 14 wherein said beveled and said angular peripheries of said rings are so related that said inner sealing ring is positioned to protrude beyond both said obturating and said outer sealing rings to effect a wiping action on the breech end face of the gun tube during the breech closing movement of the breechblock.

References Cited UNITED STATES PATENTS 3,125,928 3/1964 Bartels 8926 BENJAMIN A. BORCHELT, Primary Examiner. STEPHEN C. BENTLEY, Assistant Examiner. 

